We finally have an official Note 7’s autopsy report!
Samsung has confirmed that bad battery design and a rush to release an updated version of the phone caused some of the devices to overheat and explode. Long story short, the Note 7’s battery (The one from Samsung SDI) was too large for the phone, there wasn’t enough room between the heat-sealed protective pouch around the battery and its internals, which caused the explosion. Samsung then switched to a different battery supplier (Batteries sourced from Amperex Technology Limited), but a completely different production flaw was introduced — some cells were missing insulation tape, and some batteries had sharp protrusions inside the cell that led to damage to the separator between the anode and cathode.
They’ve also released an infographic that seeks to explain the whole problem in detail:
Moving forward, Samsung plans to assign teams to own the crucial final checks for each device’s core component, and putting batteries through an 8-point test which includes durability testing, visual inspection, x-rays, charge and discharge tests, tests of total volatile organic compounds (TVOC), disassembling tests, accelerated usage tests, and open circuit voltage.